Display device and electronic apparatus

ABSTRACT

A display unit includes sub-pixels that each have a light emitting element, a capacitor, a first transistor that writes a video signal potential to the capacitor, and a second transistor that provides a drive current to the light emitting element based on a voltage stored in the capacitor. Each first transistor has a channel width W and channel length L, such that a width to length ratio is W/L. The width to length ratio W 1 /L 1  of one of the first transistors is different than a width-to-length ratio W 2 /L 2  of at least one other of the first transistors.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Priority PatentApplication JP 2014-108861 filed May 27, 2014, the entire contents ofwhich are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a display device and an electronicapparatus, and particularly to a flat panel type display device and anelectronic apparatus including the display device.

BACKGROUND ART

As a flat panel type display device (flat display), a liquid crystaldisplay device (LCD), an organic electro luminescence (EL) displaydevice, or the like is known. In addition, as one of drive methods ofthe flat panel type display device, there is an active matrix method. Ina display device of the active matrix method (type), a unit pixel(hereinafter, may be simply referred to as “pixel”) including a lightemitting unit (light emitting element) includes at least a writingtransistor that writes a signal (for example, PTL 1).

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No.2007-310311

SUMMARY Technical Problem

However, in a display device of an active matrix method, for example,when a pattern of high brightness is partially displayed in a gray area,brightness of a gray pixel on a line (pixel row) including a pattern ofhigh brightness is higher than brightness of a gray pixel other thanthat (gray area). This is because a large current instantaneously flowsat the time of signal writing to a power supplying line which supplies apixel with a current, when there are many pixels of high brightnesslight emission in pixels on the same line. Accordingly, a gray pixel ona line including a pattern of high brightness is brighter than a graypixel of a gray area, and thus it can be viewed as crosstalk.

It is desirable to provide a display device which can reduce crosstalkcaused by a current instantaneously flowing through a power supplyingline at the time of signal writing, and to provide an electronicapparatus including the display device.

Solution to Problem

The present disclosure provides various exemplary embodiments that solveat least the above-noted problems. One exemplary embodiment of thepresent disclosure includes a display unit comprising: a plurality ofsub-pixels, each including a light emitting element, a capacitor, afirst transistor configured to write a signal potential to thecapacitor, and a second transistor configured to provide a drive currentto the light emitting element based on a voltage stored in thecapacitor. The first transistor of each of the plurality of sub-pixelsmay have a width-to-length ratio W/L, and a width to length ratio W₁/L₁of a first sub-pixel of the plurality of sub-pixels may be differentthan a width-to-length ratio W₂/L₂ of a second sub-pixel of theplurality of sub-pixels.

Another exemplary embodiment of the present disclosure includes anelectronic apparatus comprising a display unit comprising: a pluralityof sub-pixels, each including a light emitting element, a capacitor, afirst transistor configured to write a signal potential to thecapacitor, and a second transistor configured to provide a drive currentto the light emitting element based on a voltage stored in thecapacitor. The first transistor of each of the plurality of sub-pixelsmay have a width-to-length ratio W/L, and a width to length ratio W₁/L₁of a first sub-pixel of the plurality of sub-pixels may be differentthan a width-to-length ratio W₂/L₂ of a second sub-pixel of theplurality of sub-pixels.

Advantageous Effects of Invention

According to the embodiment of the present disclosure, since a currentinstantaneously flowing through the power supplying line at the time ofsignal writing can be reduced, it is possible to reduce crosstalk causedby the instantaneous current.

Meanwhile, the present disclosure is not limited to the effectsdescribed herein, and may have any one of the effects described in thepresent specification. In addition, the effects described in the presentspecification are simply examples, and the present disclosure is notlimited to this, and in addition, may have an additional effect.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a system configuration diagram schematically illustrating abasic configuration of an active matrix type display device to which atechnology of the present disclosure is applied.

FIG. 2 is a circuit diagram illustrating an example of a specificcircuit configuration of a unit pixel (pixel circuit).

FIG. 3 is a timing waveform diagram illustrating a basic circuitoperation of an organic EL display device to which a technology of thepresent disclosure is applied.

FIG. 4A is a view illustrating a mechanism that is visually recognizedas cross-talk, and particularly illustrates a display pattern example,and FIG. 4B is a view illustrating a mechanism that is visuallyrecognized as cross-talk, and particularly illustrates an image in whichthe cross-talk occurs.

FIG. 5 is a waveform diagram illustrating drive waveforms at the time ofsignal writing performed by a writing transistor.

FIG. 6 is a diagram illustrating an image of a current flowing through adrive transistor when cross talk occurs.

FIG. 7A is a plan view illustrating an example of a configuration of awriting transistor, and particularly illustrates a configuration of atransistor that serves as a reference, FIG. 7B is a plan viewillustrating an example of a configuration of a writing transistor, andparticularly illustrates a configuration of a transistor in which an Llength is changed, and FIG. 7C is a plan view illustrating an example ofa configuration of a writing transistor, and particularly illustrates aconfiguration of a transistor in which a W length is changed, and FIG.7D is a plan view illustrating an example of a configuration of awriting transistor, and particularly illustrates a configuration of atransistor in which an L length and a W length are changed together.

FIG. 8A is a view illustrating a color arrangement of a sub-pixelaccording to Example 1, and FIG. 8B is a view illustrating a colorarrangement of a sub-pixel according to Example 2.

FIG. 9 is a waveform diagram illustrating drive waveforms at the time ofsignal writing performed by a writing transistor, in a case of Example1.

FIG. 10 is a perspective view illustrating an appearance of a televisionset that is an example of an electronic apparatus according to thepresent disclosure.

DESCRIPTION OF EMBODIMENTS

Hereinafter, forms (hereinafter, referred to as “embodiment”) forperforming a technology of the present disclosure will be described indetails with reference to the drawings. The technology of the presentdisclosure is not limited to the embodiments, various numerical valuesor the like of the embodiments are exemplified. In the followingdescription, the same symbols or reference numerals will be attached tothe same elements or elements having the same function, and repeateddescription will be omitted. Meanwhile, the description will be made inthe following sequence.

1. Total Description with regard to Display Device and ElectronicApparatus of Present Disclosure

2. Display Device to which Technology of Present Disclosure is Applied

2-1. System Configuration

2-2. Pixel Circuit

2-3. With Regard to Crosstalk due to Instantaneous Current at the timeof Signal Writing

3. Description of Embodiment

3-1. Example 1 [Example of Vertical Stripe Arrangement of RGB of ColorArrangement of Sub-pixel]

3-2. Example 2 [Example of Character Arrangement of Field of RGBW ofColor Arrangement of Sub-pixel]

4. Modification Example

5. Electronic Apparatus (Example of Television Set)

<Total Description with Regard to Display Device and ElectronicApparatus of Present Disclosure>

In a display device and an electronic apparatus, when a unit pixel isconfigured by sub-pixels with a plurality of colors, a color unit of thesub-pixel can be differently configured, with regard to a size of awriting transistor connected to one scanning line in each unit pixel.

In the display device and the electronic apparatus according to thepresent disclosure which include a desirable configuration describedabove, when a unit pixel is configured by sub-pixels with a plurality ofcolors, a color unit of the sub-pixel can be differently configured,with regard to a size of a writing transistor connected to one scanningline in each unit pixel. In addition, a size of a writing transistor ofa sub-pixel of each color that configures a unit pixel can be configuredto be set to sizes different from each other in correspondence to acurrent value which is necessary at the time of signal writing.

In addition, in the display device and the electronic apparatusaccording to the present disclosure, which include a desirableconfiguration described above, a size of a writing transistor in asub-pixel of each color that configures a unit pixel, can be configuredto be set such that a size is increased in a sequence that a currentvalue necessary at the time of signal writing is decreased. In addition,even when the unit pixel has a red sub-pixel, a green sub-pixel, and ablue sub-pixel in addition to a white sub-pixel, sizes of the writingtransistor of each sub-pixel can be configured to be set so as to beincreased in a sequence of the white sub-pixel, the red sub-pixel, thegreen sub-pixel, and the blue sub-pixel.

Alternatively, in the display device and the electronic apparatusaccording to the present disclosure which include a desirableconfiguration described above, when the unit pixel includes a drivetransistor that drives a light emitting unit based on a signal that iswritten by the writing transistor, the unit pixel is configured to havea correction function to correct variation of a drive current caused byvariation of characteristics of the drive transistor. The correctionfunction can be configured to correct variation of a drive currentcaused by variation of a threshold voltage of the drive transistor. Inaddition, the correction function can be configured to correct variationof a drive current caused by variation of mobility of a semiconductorthin film that configures a channel of the drive transistor.

In addition, in the display device and the electronic apparatusaccording to the present disclosure which include a desirableconfiguration described above, a light emitting unit of a unit pixel canbe configured with a current drive type electro-optical element, forexample, an organic electro luminescence (EL) element. The organic ELelement is a self light emitting type electro-optical element (lightemitting element) that uses electroluminescence of an inorganicmaterial, and uses a phenomenon in which light is emitted if an electricfield is applied to an organic thin film. As a current drive typeelectro-optical element, an inorganic EL element, an LED element, asemiconductor laser element, or the like can be used in addition to anorganic EL element.

An organic EL element has a configuration in which an organic layer isformed by sequentially depositing a hole transport layer, a lightemitting layer, an electron transport layer, and an electron injectionlayer on a first electrode (for example, anode), and a second electrode(for example, cathode) is formed on the organic layer. Then, by applyinga DC voltage between the first electrode and the second electrode, holesare injected into the light emitting layer via the hole transport layerfrom the first electrode (anode), electrons are injected into the lightemitting layer via the electron transport layer from the secondelectrode (cathode), and light is emitted when the electrons and theholes are recombined in the light emitting layer.

An organic EL display device that uses an organic EL element as a lightemitting unit of a pixel has the following characteristics. That is,since the organic EL element can be driven by an application voltageequal to or less than 10 V, the organic EL display device consumes a lowpower. Since the organic EL element is a self light emitting typeelement, the organic EL display device has high visibility of an image,compared to a liquid crystal display device which is the same flat typedisplay device, and furthermore, since an illumination member such as abacklight is not necessary, it is easy to reduce weight and to make thinFurthermore, since a response speed of an organic EL element is veryfast as a few microseconds, afterimage at the time of displaying amoving image does not occur in the organic EL display device.

<Display Device to which Technology of Present Disclosure is Applied>

(System Configuration)

FIG. 1 is a system configuration diagram schematically illustrating abasic configuration of an active matrix type display device (displaydevice of the present disclosure) to which a technology of the presentdisclosure is applied.

The active matrix type display device is a display device in which anoperation of a light emitting unit (light emitting element) is performedby an active element that is provided in a pixel which is the same asthe light emitting unit, for example, insulating gate type field effecttransistor. A thin film transistor (TFT) is typically used as theinsulating gate type field effect transistor.

Here, as an example, an active matrix type organic EL display devicewhich uses an organic EL element as a light emitting unit (lightemitting element) of a unit pixel (pixel circuit) will be described. Theorganic EL element is a current drive type electro-optical element inwhich light emission brightness is changed depending on a current valueflowing through a device. Hereinafter, a “unit pixel/pixel circuit” mayalso be simply referred to as a “pixel”. A thin film transistor is usedfor controlling a peripheral circuit which will be described later, inaddition to being used for controlling a pixel.

As illustrated in FIG. 1, an organic EL display device 10 to which atechnology of the present disclosure is applied, is configured toinclude a pixel array unit 30 in which a plurality of unit pixels 20 aretwo-dimensionally arranged in a matrix, and a drive unit (periphery)which is disposed in a peripheral area of the pixel array unit 30 anddrives the pixels 20. The drive unit is configured with, for example, awriting scanning unit 40, a power supplying scanning unit 50, a signaloutput unit 60, and the like, and drives each pixel 20 of the pixelarray unit 30.

In the present example, the writing scanning unit 40, the powersupplying scanning unit 50, and the signal output unit 60 are mounted onthe same substrate as the pixel array unit 30, that is, on a displaypanel 70. However, it is also possible to adopt a configuration in whichsome or all of the writing scanning unit 40, the power supplyingscanning unit 50, and the signal output unit 60 are provided in a memberother than the display panel 70. In addition, the writing scanning unit40 and the power supplying scanning unit 50 are respectively disposed inone side of the pixel array unit 30, but it is also possible to adopt aconfiguration in which the writing scanning unit 40 and the powersupplying scanning unit 50 are disposed in both sides of the pixel arrayunit 30 which is interposed therebetween. As a substrate of the displaypanel 70, a transparent insulating substrate such as a glass substratecan also be used, and a semiconductor substrate such as a siliconsubstrate can also be used.

Here, when the organic EL display device 10 performs a color display,one pixel (unit pixel/pixel) that is a unit forming a color image isconfigured by sub-pixels of a plurality of colors. At this time, eachsub-pixel corresponds to the pixel 20 of FIG. 1. More specifically, in adisplay device that performs a color display, for example, one pixel isconfigured by three sub-pixels of a sub-pixel that emits red (R) light,a sub-pixel that emits green (G) light, and a sub-pixel that emits blue(B) light.

However, the one pixel is not the limited to a combination of sub-pixelswith three original colors of RGB, and it is also possible to configurethe one pixel by adding a sub-pixel of one color or sub-pixels of aplurality of colors to the sub-pixels with three original colors. Morespecifically, for example, it is also possible to configure the onepixel by adding a sub-pixel that emits white (W) light for increasingbrightness, or to configure the one pixel by adding at least onesub-pixel that emits complementary color light for expanding a colorreproduction range.

In the pixel array unit 30, scanning lines 31 (31 ₁ to 31 _(m)) andpower supplying lines 32 (32 ₁ to 32 _(m)) are arranged in each pixelrow in a row direction (arrangement direction of pixel of pixelrow/horizontal direction), with respect to an arrangement of m rows andn columns of pixels 20. Furthermore, signal lines 33 (33 ₁ to 33 _(n))are arranged in each pixel column in a column direction (arrangementdirection of pixel of pixel column/vertical direction), with respect toan arrangement of m rows and n columns of pixels 20.

The scanning lines 31 ₁ to 31 _(m) are respectively connected to outputterminals of corresponding rows of the writing scanning unit 40. Thepower supplying lines 32 ₁ to 32 _(m) are respectively connected tooutput terminals of corresponding rows of the power supplying scanningunit 50. The signal lines 33 ₁ to 33 _(n) are respectively connected tooutput terminals of corresponding columns of the signal output unit 60.

The writing scanning unit 40 is configured by a shift register circuitand the like. When a signal voltage of a video signal is written to eachpixel 20 of the pixel array unit 30, the writing scanning unit 40sequentially supplies writing scanning signals WS (WS₁ to WS_(m)) to thescanning lines 31 (31 ₁ o 31 _(m)), thereby sequentially scanning eachpixel 20 of the pixel array unit 30 by a row unit, that is, performingso-called line sequential scanning.

The power supplying scanning unit 50 is configured by a shift registercircuit and the like, in the same manner as the writing scanning unit40. The power supplying scanning unit 50 supplies power supplying lines32 (32 ₁ to 32 _(m)) with power supply voltages DS (DS₁ to DS_(m)) thatcan be switched by a first power supply voltage V_(ccp) and a secondpower supply voltage V_(ini) lower than the first power supply voltageV_(ccp), in synchronization with the line sequential scanning performedby the writing scanning unit 40. As will be described later, a controlof light emission/non-light-emission (light off) of the pixel 20 isperformed by switching V_(ccp)/V_(ini) of the power supply voltage DS.

The signal output unit 60 selectively outputs a signal voltage(hereinafter, may be simply referred to as “signal voltage”) V_(sig) ofa video signal, which is supplied from a signal supply source (notillustrated), according to brightness information, and a referencevoltage V_(ofs). Here, the reference voltage V_(ofs) is a voltage (forexample, voltage corresponding to a black level of video signal) thatserves as a reference of the signal voltage V_(sig) of the video signal,and is used at the time of threshold correction processing that will bedescribed later.

The signal voltage V_(sig) and the reference voltage V_(ofs) that areoutput from the signal output unit 60 are written to each pixel 20 ofthe pixel array unit 30 via the signal lines 33 (33 ₁ to 33 _(n)) by aunit of pixel row that is selected by scanning performed by the writingscanning circuit 40. That is, the signal output unit 60 adopts a driveform of line sequential writing which writes the signal voltage V_(sig)by a row (line) unit.

(Pixel Circuit)

FIG. 2 is a circuit diagram illustrating an example of a specificcircuit configuration of the unit pixel (pixel circuit) 20. A lightemitting unit of the pixel 20 is configured with an organic EL element21 that is an example of a current drive type electro-optical element inwhich light emission brightness is changed depending on a current valueflowing through a device.

As illustrated in FIG. 2, the pixel 20 is configured with an organic ELelement 21, and a drive circuit that drives the organic EL element 21 bymaking a current flow through the organic EL element 21. The organic ELelement 21 has a cathode electrode that is connected to a common powersupply line 34 which is disposed in all pixels 20.

The drive circuit that drives the organic EL element 21 has a circuitconfiguration of 2Tr2C which includes a drive transistor 22, a writingtransistor 23, a storage capacitor 24, and an auxiliary capacitor 25,that is, two transistors (Tr) and two capacitance elements (C). Here,the drive transistor 22 and the writing transistor 23 use an N channeltype thin film transistor (TFT). However, as illustrated here, aconductive combination of the drive transistor 22 and the writingtransistor 23 is just an example, and the present disclosure is notlimited to this combination.

The drive transistor 22 has one electrode (source or drain electrode)connected to the power supplying lines 32 (32 ₁ to 32 _(m)) and hasanother electrode (source or drain electrode) connected to an anodeelectrode of the organic EL element 21. The writing transistor 23 hasone electrode (source or drain electrode) connected to the signal lines33 (33 ₁ to 33 _(n)) and has another electrode (source or drainelectrode) connected to a gate electrode of the drive transistor 22. Inaddition, a gate electrode of the writing transistor 23 is connected tothe scanning lines 31 (31 ₁ to 31 _(m)).

In the drive transistor 22 and the writing transistor 23, the oneelectrode indicates a metal wire that is electrically connected to oneof the source region and the drain region, and another electrodeindicates a metal wire that is electrically connected to the otherregion of the source region and the drain region. In addition, by apotential relationship between the one electrode and another electrode,if becoming a source electrode, one electrode becomes a drain electrode,and if becoming a drain electrode, another electrode becomes sourceelectrode.

The storage capacitor 24 has one electrode connected to the gateelectrode of the drive transistor 22, and has the other electrodeconnected to another electrode of the drive transistor 22 and the anodeelectrode of the organic EL element 21. The auxiliary capacitor 25 hasone electrode connected to the anode electrode of the organic EL element21, and has the other electrode connected to a cathode electrode of theorganic EL element 21. That is, the storage capacitor 24 is connected inparallel to the organic EL element 21.

In the configuration described above, the writing transistor 23 isturned on according to a writing scanning signal WS in which a state ofa high voltage that is applied from the writing scanning unit 40 to thegate electrode via the scanning line 31 becomes an active state.Accordingly, the writing transistor 23 samples the signal voltageV_(sig) of a video signal according to brightness information that issupplied from the signal output unit 60 via the signal lines 33 at adifferent timing, or the reference voltage V_(ofs), and writes thevoltage to the pixel 20. The signal voltage V_(sig) or the referencevoltage V_(ofs) that is written by the writing transistor 23 is storedin the storage capacitor 24.

When the power supply voltage DS of the power supplying line 32 (32 ₁ to32 _(m)) is the first power supply voltage V_(ccp), one electrodebecomes a drain electrode, and another electrode becomes a sourceelectrode, and thus the drive transistor 22 operates in a saturationregion. Accordingly, the drive transistor 22 receives a current from thepower supplying line 32, drives the organic EL element 21 using thecurrent, and thereby the organic EL element 21 emits light. Morespecifically, the drive transistor 22 operates in a saturation region,and supplies the organic EL element 21 with a drive current with acurrent value according to a voltage value of the signal voltage V_(sig)stored in the storage capacitor 24, and the organic EL element is drivenby a current, thus, emitting light.

Furthermore, when the power supply voltage DS is switched to the secondpower supply voltage V_(ini) from the first power supply voltageV_(ccp), one electrode becomes a source electrode, and another electrodebecomes a drain electrode, and thus the drive transistor 22 operates asa switching transistor. Accordingly, the drive transistor 22 does notsupply a drive current to the organic EL element 21 thereby the organicEL element 21 is in a non-light-emission state. That is, the drivetransistor 22 also has a function as a transistor that controls lightemission and not-light-emission of the organic EL element 21.

By the switching operation of the drive transistor 22, a time period inwhich the organic EL element 21 is in a non-light-emission state(non-light-emission period) is provided, and a ratio (duty) of a lightemission period to a non-light-emission period of the organic EL element21 can be controlled. Since afterimage blur according to light emissionof a pixel over one display frame period can be reduced by this dutycontrol, it is possible to further increase picture quality of a movingimage.

The first power supply voltage V_(ccp) of the first and second powersupply voltages V_(ccp) and V_(ini) that are selectively supplied fromthe power supplying scanning unit 50 via the power supplying line 32, isa power supply voltage for supplying the drive transistor 22 with adrive current which drives the organic EL element 21 so as to emitlight. The second power supply voltage V_(ini) is a power supply voltagefor applying a reverse bias to the organic EL element 21. The secondpower supply voltage V_(ini) is set to a voltage that is lower than thereference voltage V_(ofs), for example, a voltage that is lower than(V_(ofs)−V_(th)), when a threshold voltage of the drive transistor 22 isreferred to as V_(th), and desirably, a voltage that is sufficientlylower than (V_(ofs)−V_(th)).

Each pixel 20 of the pixel array unit 30 has a function to correctvariation of a drive current caused by variation of characteristics ofthe drive transistor 22. As the characteristics of the drive transistor22, for example, the threshold voltage V_(th) of the drive transistor22, or mobility u (hereinafter, simply referred to as “mobility u of thedrive transistor 22”) of a semiconductor fin film that configures achannel of the drive transistor 22 can be used.

Correction (hereinafter, may be referred to as “threshold correction”)of variation of the drive current caused by the variation of thethreshold voltage V_(th) can be performed by initializing a gatepotential V_(g) of the drive transistor 22 to the reference voltageV_(ofs). Specifically, an operation of changing a source potential V_(s)of the drive transistor 22 is performed toward a potential that isobtained by decreasing he threshold voltage V_(th) of the drivetransistor 22 from the initialization voltage by using theinitialization voltage (reference voltage V_(ofs)) of the gate potentialV_(g) of the drive transistor 22 as a reference. If this operation isperformed, soon, a source-gate voltage v_(gs) of the drive transistor 22is converged to the threshold voltage V_(th) of the drive transistor 22.A voltage corresponding to the threshold voltage V_(th) is stored in thestorage capacitor 24. Then, since a voltage corresponding to thethreshold voltage V_(th) is stored in the storage capacitor 24, it ispossible to reduce dependency with respect to the threshold voltageV_(th) of a drain-source current I_(ds) flowing through the drivetransistor 22, when the drive transistor 22 is driven by the signalvoltage V_(sig) of a video signal.

Meanwhile, correction (hereinafter, may be referred to as “mobilitycorrection”) of variation of a drive current caused by variation ofmobility u, is performed by making a current flow into the storagecapacitor 24 via the drive transistor 22, in a state where the writingtransistor 23 is turned on and the signal voltage V_(sig) of the videosignal is written. In other words, the correction is performed byperforming negative feedback to the storage capacitor 24 with an amountof feedback (amount of correction) according to the current I_(ds)flowing through the drive transistor 22. When the video signal iswritten, the dependency with respect to the threshold voltage V_(th) ofthe drain-source current I_(ds) is cancelled in advance by the thresholdcorrection, and the drain-source current I_(ds) depends on the mobilityu of the drive transistor 22. Thus, the negative feedback is performedto the drain-source voltage V_(ds) of the drive transistor 22 by theamount of feedback according to the current I_(ds) flowing through thedrive transistor 22, and thus it is possible to suppress the dependencywith respect to the mobility u of the drain-source current I_(ds)flowing through the drive transistor 22.

FIG. 3 is a timing waveform diagram illustrating a basic circuitoperation of the organic EL display device 10 to which a technology ofthe present disclosure is applied. The timing waveform of FIG. 3illustrates a change of each of a voltage (writing scanning signal) WSof the scanning line 31, a voltage (power supply voltage) DS of thepower supplying line 32, a voltage (V_(sig)/V_(ofs)) of the signal line33, and the source potential V_(s) and the gate potential V_(g) of thedrive transistor 22. Here, a switching period of a voltage of the signalline 33, that is, a switching period of the signal voltage V_(sig) ofthe video signal and the reference voltage V_(ofs) becomes onehorizontal period (1H).

Meanwhile, since the writing transistor 23 has an N channel type, a statof a high voltage of the writing scanning signal WS becomes an activestate, and a state of a low voltage becomes an inactive state. Then, thewriting transistor 23 is turned on in a state where the writing scanningsignal WS is active, and is turned off in a state where the writingscanning signal WS is inactive.

In the timing waveform of FIG. 3, a period before time t₁₁ is a lightemission period of the organic EL element 21 of previous display frame,and when reaching time t₁₁, the signal enters a non-light-emissionperiod of a new display frame (current display frame) of line sequentialscan. Then, a time period from time t₁₂ to time t₁₄ when the writingscanning signal WS enters an active state, becomes a writing period inwhich the writing transistor 23 writes the reference voltage V_(ofs) tothe pixel 20, and a period from time t₁₃ to time t₁₄ becomes a thresholdcorrection period in which the variation of the drive current caused bythe variation of the threshold voltage V_(th) of the drive transistor 22is corrected.

In addition, in the period from time t₁₅ to time t₁₈, a voltage of thesignal line 33 becomes the signal voltage V_(sig) of a video signal.Then, in a period from time t₁₆ to time t₁₇, the writing scanning signalWS enters an active state again, and thus the writing transistor 23 isturned on. Accordingly, the signal voltage V_(sig) of a video signal iswritten to the pixel 20 by the writing transistor 23, and mobilitycorrection processing of correcting the variation of the drive currentcaused by the variation of the mobility u of the drive transistor 22 isperformed. That is, the period from the time t₁₆ to time t₁₇ becomes(writing of the signal voltage V_(sig)+mobility correction period).Then, when reaching the time t₁₇, the signal enters a light emissionperiod of the current display frame.

(With regard to Crosstalk due to Instantaneous Current at the time ofSignal Writing)

Next, crosstalk will be described, which occurs due to a large currentthat instantaneously flows through the power supplying line 32 when thesignal voltage V_(sig) is written by the writing transistor 23. Here, asillustrated in FIG. 4A, for example, a case where a pattern (WINDOW) ofhigh brightness is partially displayed on a gray area will be described.

When a pattern of high brightness is partially displayed on a gray area,as illustrated in FIG. 4B, brightness of a gray pixel (point B in thefigure) on a line (pixel row) including a pattern of high brightness ishigher than brightness of a gray pixel (point A in the figure) otherthan that (gray area). Accordingly, a gray pixel of the point B of apattern of high brightness is brighter than the gray pixel of the pint Aof the gray area, and thus it is viewed as crosstalk.

Here, a mechanism being viewed as crosstalk will be described using thewaveform diagram of FIG. 5. FIG. 5 is a waveform diagram illustratingdrive waveforms at the time of signal writing performed by the writingtransistor 23. In FIG. 5, waveforms at the time of signal writing of thepower supply voltage DS, the writing scanning signal WS, and the gatepotential V_(g) and source potential V_(s) of the drive transistor 22are illustrated.

In addition, FIG. 6 illustrates an image of a current flowing throughthe drive transistor 22 when crosstalk occurs. FIG. 6 illustrates animage with regard to an area that is surrounded by O (VI) of dottedline, that is, an interface portion of a gray area, a pattern (WINDOW)of high brightness, and crosstalk portion, in FIG. 4B. In addition, inFIG. 6, a thick arrow indicates a state where a current is relativelylarge, and a thin arrow indicates a state where a current is relativelysmall. Here, as an example, a case where a red (R) sub-pixel, a green(G) sub-pixel, and a blue (B) sub-pixel are arranged in a verticalstripe manner is illustrated.

When the writing scanning signal WS for signal writing is applied to thewriting transistor 23, mobility correction is started, and thereby acurrent flows through the drive transistor 22. This current is suppliedfrom the power supplying line 32, but timings when the writing scanningsignal WS is applied to all pixels in which the drive transistors 22 areconnected to the power supplying line 32 are the same, and thus currentssimultaneously flow through each pixel. Then, when there are many pixelsof high brightness light emission among the pixels connected to the samepower supplying line 32, a large current instantaneously flows throughthe power supplying line 32, and according to this, a voltage of thepower supplying line 32, that is, a voltage drop occurs in the powersupply voltage DS. The voltage drop is determined by a current flowingthrough the power supplying line 32 and a wiring resistance of the powersupplying line 32.

Accordingly, when a gray pixel of the point A and a gray pixel of thepoint B in FIG. 4B are compared to each other, there is a pixel throughwhich a large current with high brightness flows, among the pixels onthe line (pixel row) including gray pixels of the point B, and thus avoltage drop of the power supplying line 32 at the time of signalwriting performed by the writing transistor 23 is larger in the graypixel of the point A than in the gray pixel of the point B. Since thepower supplying line 32 is connected to a power supply, the temporaryvoltage drop is gradually recovered, and rises up to (V _(ccp)-(voltagedrop of current flowing at the time of normal light emission).

If the writing scanning signal WS enters an inactive state and thewriting transistor 23 is turned off, a gate node of the drive transistor22 is floated. For this reason, if a potential of the power supplyingline 32 connected to the drain electrode of the drive transistor 22increases, the gate potential V_(g) of the drive transistor 22 alsoincreases via a gate-drain capacitance C_(gd) of the drive transistor22.

After entering an inactive state, and until the writing scanning signalWS enters a light emission normal state, and when the potential of thepower supplying line 32 increases by delta V, an amount of change deltaV_(g) of the gate potential V_(g) of the drive transistor 22 isrepresented by the following equation.

delta V _(g)=delta V*C _(gs)/C _(g) _(_) _(total)

Here, C_(g) _(_) _(total) is a total sum of all capacitances that areconnected (viewed from the gate node) to the gate node of the drivetransistor 22. Specifically, if a capacitance of the storage capacitor24 is referred to as C_(s), a capacitance between the gate and source ofthe drive transistor 22 is referred to as C_(gs), an equivalentcapacitance of the organic EL element 21 is referred to as C_(oled), acapacitance of the auxiliary capacitor 25 is referred to as C_(sub), acapacitance between the gate-source and the drain of the writingtransistor 23 is referred to as C_(ws), and a capacitance between thegate and the drain of the drive transistor 22 is referred to as C_(gd),C_(g) _(_) _(total) is represented by the following equation.

C_(g) _(_) _(total)={(C _(s) +C _(gs))(C _(sub) +C _(oled))/(C _(s) +C_(gs) +C _(oled) +C _(sub))}+C _(ws) +C _(gd)

If the gate potential V_(g) of the drive transistor 22 increases bydelta V_(g), the source potential V_(s) of the drive transistor 22increases by the following equation.

delta V _(s)=delta V _(g)(C_(s) +C _(gd))/(C _(s) +C _(gs) +C _(oled) +C_(sub))

If the gate potential V_(g) of the drive transistor 22 increases andaccording to this, the source potential V_(s) of the drive transistor 22also increases, an amount of change delta V_(gs) of the gate-sourcevoltage V_(gs) of the drive transistor 22 is represented by thefollowing equation.

delta V _(gs)=delta V _(g)-delta V _(s)

Here, if there is almost no drop in a potential of the power supplyingline 32 connected to the gray pixel of the point A, the gate-sourcevoltage V_(gs) of the drive transistor 22 increases by an amount ofchange delta V_(gs) of the gate-source voltage V_(gs) of the drivetransistor 22, and the drive current I_(ds) also increases. Thus, themore the drive current I_(ds) increases, the higher the brightnessbecomes. Thus, since the gray pixel of the point B has high brightnesscompared to the gray pixel of the point A, it is viewed as crosstalk,and causes deterioration of uniformity (uniformity of screen). Acrosstalk rate is determined by a ratio of the gate-source voltagesV_(gs) on a display line and a non-display line of a pattern (WINDOW) ofhigh brightness.

<Description of Embodiment>

Subsequently, an embodiment of the present disclosure will be described.As can be seen from the above description, the crosstalk which causesdeterioration of uniformity occurs due to the current intensivelyflowing through the power supplying line 32 when the signal voltageV_(sig) is written by the writing transistor 23. Thus, a peak currentflowing through the drive transistor 22 connected to one power supplyingline 32 for each pixel 20 may be dispersed between the pixels 20. Atechnology of the present disclosure is provided in view of this point.

The embodiment of the present disclosure adopts a configuration in whichtransistors having a transistor size, that is, W (channel width)/L(channel length) different from each other are included, among thewriting transistors 23 connected to one scanning line 31 for each pixel20. Here, the fact that the writing transistors 23 connected to onescanning line 31 for each pixel 20 includes transistors having differentsizes from each other means that the sizes of the writing transistors 23connected to one scanning line 31 are not uniform.

Thus, the writing transistors 23 connected to one scanning line 31include transistors having the same size and transistors havingdifferent sizes from each other. Here, “the same size” means that thesize is substantially the same, in addition to that the size is exactlythe same, and the presence of various variations occurring in the designor in the manufacture is acceptable. That is, a difference in sizeoccurring due to various variations in the design or the manufacturingis not included in concept of the different size in the presentdisclosure. Regularity with regard to arrangement of the transistorshaving different sizes from each other does not matter in one pixel row(line).

When the size of the writing transistor 23 is changed, an L length, a Wlength, or both the L length and the W length may be changed.Specifically, when an L length of a transistor which is a reference isreferred to as L₀ and a W length is referred to as W₀ as illustrated inFIG. 7A, the L length is set to L₁ shorter than the reference L₀ asillustrated in FIG. 7B, or the L length is set to W₁ longer than thereference W₀ as illustrated in FIG. 7C. Alternatively, the L length isset to L₂ shorter than the reference L₀, and the W length is set to W₂longer than the reference W₀ as illustrated in FIG. 7D.

Here, if the gate-source voltage of the writing transistor 23 isreferred to as V_(g) _(_) _(ws) and the threshold voltage is referred toas V_(th) _(_) _(ws), the drain-source current I_(ds) _(_) _(ws) of thewriting transistor 23 is represented by the following equation.

I _(ds) _(_) _(ws) =k(V _(gs) _(_) _(ws) −V _(th) _(_) _(ws))²

k is an integer which is determined by a device structure, temperature,and a voltage, and is a value approximately proportional to (W/L). Thus,when a bias voltage is the same, the wider the W length is, or theshorter the L length is, the larger the drain-source current I_(ds) _(_)_(ws) of the writing transistor 23 is, and thus it is possible toincrease a drive capability of a transistor.

In the present disclosure, the pixel 20 may be a monochrome pixel, andmay be a pixel that is unit forming a color image, that is, a unit pixelthat is configured by sub-pixels of a plurality of colors. Hereinafter,a case where the pixel 20 is configured by a pixel that is unit pixelforming a color image will be uses as an example, and a specific examplewill be described.

EXAMPLE 1

FIG. 8A is a view illustrating a color arrangement of a sub-pixelaccording to Example 1. In a color arrangement of Example 1, sub-pixelsconfiguring the pixel 20 are formed of sub-pixels of three colors of red(R), green (G), and blue (B), and these sub-pixels have a verticalstripe shape in which the sub-pixels are arranged in a strip shape incolumn direction (vertical direction). Then, in Example 1, when thepixel 20 is configured by a pixel which is unit forming a color image,that is, configured by sub-pixels of three colors of RGB, the size (W/L)of the writing transistor 23 connected to one scanning line 31 for eachsub-pixel is set so as to be changed by a color unit.

By changing the size (W/L) of the writing transistor 23, the drivecapability of the transistor is changed, and thus it is possible todisplace writing timing of the writing transistor 23 by a color unit ofthe sub-pixel. FIG. 9 illustrates drive waveforms at the time of signalwriting performed by the writing transistor 23, in a case of Example 1.As an example, Example 1 adopts a configuration in which the size (W/L)of the writing transistor 23 of a sub-pixel of G is set to be greaterthan the size of the writing transistor 23 of a sub-pixel of R.

If the size (W/L) of the transistor is large, a drive capabilityincreases as a transistor, and thus a writing speed of the writingtransistor 23 is increased. Thus, the peak of a current of the sub-pixelof G also becomes faster than the peak of a current of the sub-pixel ofR. When the size of the writing transistor 23 is not changed for eachcolor, a peak position of a current of the sub-pixel of G is the same asa peak position of a current of the sub-pixel of R as illustrated bydotted line in FIG. 9, and thus a large current instantaneously flowsthrough the power supplying line 32.

In contrast to this, in Example 1 in which the size of the writingtransistor 23 is changed for each color, a peak position of a currentflowing through the drive transistor 22 connected to one power supplyingline 32 for each sub-pixel can be dispersed between sub-pixels of eachcolor. Accordingly, an absolute value of a current instantaneouslyflowing through the power supplying line 32 can be reduced, and thus itis possible to decrease a voltage drop on the power supplying line 32.Then, an amount of voltage increase delta V′ of a potential on the powersupplying line 32 from when the writing scanning signal WS enters aninactive state until becoming normal light emission state, is smallerthan an amount of voltage increase delta V when the size of the writingtransistor 23 is not changed for each color. As a result, at the time ofsignal writing performed by the writing transistor 23, it is possible toreduce crosstalk caused by a current instantaneously flowing through thepower supplying line 32.

Meanwhile, Example 1 has a configuration in which the sizes of thewriting transistors 23 of the sub-pixel of G and the sub-pixel of R arechanged, but in a case of a vertical stripe arrangement of the sub-pixelof three colors of RGB, it is possible to configure to change a size ofonly one color, or to change all three colors, that is, the size of thewriting transistor 23 for each color.

EXAMPLE 2

FIG. 8B is a view illustrating a color arrangement of a sub-pixelaccording to Example 2. In the color arrangement of Example 2, thesub-pixels configuring the pixel 20 are configured by sub-pixels of fourcolors including a white (W) sub-pixel in addition to the sub-pixel ofRGB, and these sub-pixels are formed of a field shape arrangement whichis arranged in a field shape. Then, also in Example 2, size (W/L) of thewriting transistor 23 connected to one scanning line 31 for each pixel20 is set so as to be changed by a color unit, in the same manner as inExample 1. Accordingly, also in Example 2, it is possible to obtain thesame actions and effects as in Example 1, that is, at the time of signalwriting performed by the writing transistor 23, a currentinstantaneously flowing through the power supplying line 32 can bereduced, and thus it is possible to reduce crosstalk caused by theinstantaneous current.

When the size of the writing transistor 23 is changed by a color unit,with regard to all sub-pixels of four colors of RGBW, that is, it ismost effective to configure such that the size of the writing transistor23 is changed for each color, but the present disclosure is not limitedto this. For example, the sub-pixel may be configured such that the sizeof the writing transistor 23 is changed for every two colors as a pair,alternatively, may be configured such that the size of the writingtransistor 23 of a sub-pixel of only one color is changed. As a example,the size of the writing transistor 23 of a sub-pixel of W is set to besmaller than the size of the writing transistor of a sub-pixel of atleast another color. Meanwhile, the color arrangement illustrated inFIG. 7B is an example, and is not limited to this, and may be a verticalstripe arrangement of sub-pixels of four colors of RGBW.

The size of the writing transistor 23 is set so as to be different sizesaccording to a current value necessary at the time of signal writingperformed by the writing transistor 23. At this time, it is preferablethat the size is set so as to be increased in a sequence of smallcurrent value necessary at the time of signal writing performed by thewriting transistor 23, with regard to the size of the writing transistor23 of sub-pixels of each color. As an example, in a case of a verticalstripe arrangement of sub-pixels of four colors of RGBW, the size is setso as to be increased in a sequence of a sub-pixel of W, a sub-pixel ofR, a sub-pixel of G, and a sub-pixel of B, with regard to the size (W/L)of the writing transistor 23 of each sub-pixel of RGBW.

<Modification Example>

In the above-described embodiment, a case where the light emitting unitof the unit pixel 20 is applied to an organic EL display device which isconfigured with the organic EL element 21 is used as an example, but thepresent disclosure is not limited to an application to the organic ELdisplay device. That is, the technology of the present disclosure can beapplied to the entire display device which is configured to have awriting transistor in which the unit pixel 20 writes a signal, such as adisplay device in which the light emitting unit of the unit pixel 20 isconfigured by a current drive type electro-optical element, such as aninorganic EL element, an LED element, or a semiconductor laser element,or a liquid crystal display device.

In addition, in the above-described embodiment, a circuit configurationof 2Tr2C is exemplified as a drive circuit that drives the organic ELelement 21, but the present disclosure is not limited to the circuitconfiguration of 2Tr2C. For example, the auxiliary capacitor 25 is justfor assisting an equivalent capacitance of the organic EL element 21,and is not a necessary configuration element. Thus, when an equivalentcapacitance of the organic EL element 21 can be sufficiently secured, itis also possible to adopt a circuit configuration of 2Tr1C except forthe auxiliary capacitor 25.

Furthermore, it may be possible to increase the number of transistors ifnecessary. As an example, it is possible to have not only aconfiguration in which the reference voltage V_(ofs) is incorporated bythe writing transistor 23 from the signal line 33, but also aconfiguration in which a dedicated switching transistor is provided, andthe reference voltage V_(ofs) is incorporated by the switchingtransistor. In addition, it is possible to have a configuration in whichswitching transistors are connected in series to the drive transistor22, and light emission/non-light-emission of the organic EL element 21is controlled by the switching transistor.

<Electronic Apparatus>

The display device of the present disclosure described above can be usedas a display unit (display device) of an electronic apparatus of allareas in which a video signal which is input to the electronicapparatus, or a video signal generated in the electronic apparatus isdisplayed as an image or a video. As an example, the display device ofthe present disclosure can be used as a display unit of an electronicapparatus for example, a television set, a digital camera, a node typepersonal computer, a portable terminal device such as a smart phone or atelephone, a video camera, and a video camera.

In this way, the display device of the present disclosure is used as adisplay unit of electronic apparatus of all areas, and thereby it ispossible to increase display quality of various electronic apparatuses.That is, as can be seen from the embodiments described above, accordingto the display device of the present disclosure, at the time of signalwriting performed by a writing transistor, it is possible to reducecrosstalk caused by a current instantaneously flowing through a powersupplying line. Thus, the display device of the present disclosure isused for the various electronic apparatuses, it is possible to increaseimage quality.

The display device of the present disclosure includes a device having amodule shape with a sealed configuration. As an example, a displaymodule formed by attaching a counter unit such as a transparent glass toa pixel array unit corresponds to the device. Meanwhile, the displaymodule may include a circuit unit, a flexible printed circuit (FPC), orthe like which inputs and outputs a signal or the like to a pixel arrayunit from the outside. Hereinafter, as a specific example of anelectronic apparatus using the display device of the present disclosure,a television set is exemplified. However, a specific example exemplifiedherein is just an example, and the present disclosure is not limited tothis.

<Specific Example>

FIG. 10 is a perspective view illustrating an appearance of a televisionset that is an example of an electronic apparatus according to thepresent disclosure. A television set 100 according to a specific exampleincludes a video display screen unit 101 which is configured by a frontpanel 102, a filter glass 103, or the like. In the television set 100,the display device of the present disclosure can be used as the videodisplay screen unit 101.

That is, the television set 100 according to a specific example ismanufactured by using the display device of the present disclosure asthe video display screen unit 101. In this way, in the television set100, the display device of the present disclosure is used as the videodisplay screen unit 101, and thereby it is possible to reduce crosstalkcaused by a current instantaneously flowing through a power supplyingline at the time of signal writing, and thus image quality is increased.

Meanwhile, the present disclosure can include at least the followingconfigurations.

(1) A display unit comprising:

-   -   a plurality of sub-pixels, each including a light emitting        element, a capacitor, a first transistor configured to write a        signal potential to the capacitor, and a second transistor        configured to provide a drive current to the light emitting        element based on a voltage stored in the capacitor,    -   wherein the first transistor of each of the plurality of        sub-pixels has a width-to-length ratio W/L, and    -   a width to length ratio W₁/L₁ of a first sub-pixel of the        plurality of sub-pixels is different than a width-to-length        ratio W₂/L₂ of a second sub-pixel of the plurality of        sub-pixels.

(2) The display unit of 1,

-   -   wherein the plurality of sub-pixels are arranged in a matrix of        rows and columns, and    -   the first sub-pixel and the second sub-pixel are located in a        same row as one another.

(3) The display unit of any one of (1) and (2), further comprising:

-   -   scanning lines, each being connected to respective gate        electrodes of the first transistors of some of the plurality of        sub-pixels,    -   wherein the first transistor of the first sub-pixel and the        first transistor of the second sub-pixel are connected to the        same scanning line as one another.

(4) The display unit of any one of (1) through (3),

-   -   wherein the first sub-pixel emits light of a first color and the        second sub-pixel emits light of a second color.

(5) The display unit of any one of (1) through (4),

-   -   wherein the first color is red and the second color is green.

(6) The display unit of any one of (1) through (5),

-   -   wherein the first color is white and the second color is green.

(7) The display unit of any one of (1) through (6),

-   -   wherein a width-to-length ratio of each of the plurality of        sub-pixels that emits light of the first-color equals W₁/L₁, and    -   a width-to-length ratio of each of the plurality of sub-pixels        that emits light of the second-color equals W₂/L₂.

(8) The display unit of any one of (1) through (7),

-   -   wherein the plurality of sub-pixels each emit light in one of N        colors, where N>1,    -   each of the N colors has a different width-to-length ratio        W_(i)/L_(i) corresponding thereto,    -   where i={1, 2, . . . , N}, and    -   for each of the N colors, a width-to-length ratio of each of the        plurality of sub-pixels that emits light of the i-th color        equals W_(i)/L_(i).

(9) The display unit of any one of (1) through (8),

-   -   wherein the N colors include white, red, green, and blue,    -   a width-to-length ratio W₁/L₁ corresponds to white, a        width-to-length ratio W₂/L₂ corresponds to red, a        width-to-length ratio W₃/L₃ corresponds to green, a        width-to-length ratio W₄/L₄ corresponds to blue, and    -   W₁/L₁<W₂/L₂<W₃/L₃<W₄/L₄.

(10) The display unit of any one of (1) through (8),

-   -   wherein the N colors include red, green, and blue,    -   a width-to-length ratio W₁/L₁ corresponds to red, a        width-to-length ratio W₂/L₂ corresponds to green, and a        width-to-length ratio W₃/L₃ corresponds to blue, and    -   W₁/L₁<W₂/L₂<W₃/L₃.

(11) An electronic apparatus comprising:

-   -   a display unit that includes a plurality of sub-pixels, each        including a light emitting element, a capacitor, a first        transistor configured to write a signal potential to the        capacitor, and a second transistor configured to provide a drive        current to the light emitting element based on a voltage stored        in the capacitor,    -   wherein the first transistor of each of the plurality of        sub-pixels has a width-to-length ratio W/L, and    -   a width to length ratio W₁/L₁ of a first sub-pixel of the        plurality of sub-pixels is different than a width-to-length        ratio W₂/L₂ of a second sub-pixel of the plurality of        sub-pixels.

(12) The electronic apparatus of (11),

-   -   wherein the plurality of sub-pixels are arranged in a matrix of        rows and columns, and    -   the first sub-pixel and the second sub-pixel are located in a        same row as one another.

(13) The electronic apparatus of any one of (11) and (12), furthercomprising:

-   -   scanning lines, each being connected to respective gate        electrodes of the first transistors of some of the plurality of        sub-pixels,    -   wherein the first transistor of the first sub-pixel and the        first transistor of the second sub-pixel are connected to the        same scanning line as one another.

(14) The electronic apparatus of any one of (11) through (13),

-   -   wherein the first sub-pixel emits light of a first color and the        second sub-pixel emits light of a second color.

(15) The electronic apparatus of any one of (11) through (14),

-   -   wherein the first color is red and the second color is green.

(16) The electronic apparatus of any one of (11) through (15),

-   -   wherein the first color is white and the second color is green.

(17) The electronic apparatus of any one of (11) through (16),

-   -   wherein a width-to-length ratio of each of the plurality of        sub-pixels that emits light of the first-color equals W₁/L₁, and    -   a width-to-length ratio of each of the plurality of sub-pixels        that emits light of the second-color equals W₂/L₂.

(18) The electronic apparatus of any one of (11) through (17),

-   -   wherein the plurality of sub-pixels each emit light in one of N        colors, where N>1,    -   each of the N colors has a different width-to-length ratio        W_(i)/L_(i) corresponding thereto,    -   where i={1, 2, . . . , N}, and    -   for each of the N colors, a width-to-length ratio of each of the        plurality of sub-pixels that emits light of the i-th color        equals W_(i)/L_(i).

(19) The electronic apparatus of any one of (11) through (18),

-   -   wherein the N colors include white, red, green, and blue,    -   a width-to-length ratio W₁/L₁ corresponds to white, a        width-to-length ratio W₂/L₂ corresponds to red, a        width-to-length ratio W₃/L₃ corresponds to green, a        width-to-length ratio W₄/L₄ corresponds to blue, and    -   W₁/L₁<W₂/L₂<W₃/L₃<W₄/L₄.

(20) The electronic apparatus of any one of (11) through (18),

-   -   wherein the N colors include red, green, and blue,    -   a width-to-length ratio W₁/L₁ corresponds to red, a        width-to-length ratio W₂/L₂ corresponds to green, and a        width-to-length ratio W₃/L₃ corresponds to blue, and    -   W₁/L₁<W₂/L₂<W₃/L₃.

(21) A display device including:

-   -   unit pixels which include light emitting units and are arranged        in a matrix,    -   in which the unit pixel includes a writing transistor that        writes a signal according to a scanning signal which is supplied        via a scanning line arranged in each pixel row, and    -   in which the writing transistors connected to one scanning line        for each unit pixel include transistors having different size        from each other.

(22) The display device described in (21),

-   -   in which the unit pixel is configured by sub-pixels of a        plurality of colors, and    -   in which the sizes of the writing transistors connected to the        one scanning line for each unit pixel are different by color        unit of the sub-pixels.

(23) The display device described in (22),

-   -   in which the unit pixel includes a white sub-pixel, and    -   in which the size of the writing transistor of the white        sub-pixel is set to be smaller than a size of a writing        transistor of a sub-pixel of at least one color.

(24) The display device described in (22) or (23), in which the sizes ofthe writing transistors of sub-pixels of each color that configure theunit pixel are set to sizes different from each other according to acurrent value necessary at the time of signal writing.

(25) The display device described in (24), in which the sizes of thewriting transistors of sub-pixels of each color that configure the unitpixel are set so as to be increased in a sequence of a small currentvalue necessary at the time of signal writing.

(26) The display device described in (25),

-   -   in which the unit pixel includes the red sub-pixel, the green        sub-pixel, and the blue sub-pixel, in addition to the white        sub-pixel, and    -   in which the sizes of the writing transistors of each sub-pixel        are set to be increased in a sequence of a white sub-pixel, a        red sub-pixel, a green sub-pixel, and a blue sub-pixel.

(27) The display device described in any one of (21) to (26), in whichthe unit pixel includes a drive transistor that drives the lightemitting unit based on a signal which is written by the writingtransistor, and includes a correction function of correcting variationof a drive current caused by variation of characteristics of the drivetransistor.

(28) The display device described in (27), in which the correctionfunction is a function of correcting the variation of the drive currentcaused by variation of a threshold voltage of the drive transistor.

(29) The display device described in (27) or (28), in which thecorrection function is a function of correcting the variation of thedrive current caused by variation of mobility of a semiconductor thinfilm that configures a channel of the drive transistor.

(30) The display device described in any one of (21) to (29), in whichthe light emitting unit of the unit pixel is configured by a currentdrive type electro-optical element.

(31) The display device described in (30), in which the current drivetype electro-optical element is an organic electroluminescence element.

(32) An electronic apparatus including:

-   -   a display device that includes unit pixels which include light        emitting units and are arranged in a matrix, in which the unit        pixel includes a writing transistor that writes a signal        according to a scanning signal which is supplied via a scanning        line arranged in each pixel row, and in which the writing        transistors connected to one scanning line for each unit pixel        include transistors having different size from each other.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

In the appended claims, ratios of channel width to channel length arereferred to using the labels W_(i)/L_(i) where i is an indexdistinguishing different ratios from one another. For example, a firstwidth to length ratio may be labeled W₁/L₁, while a second width tolength ratio that is different from the first width to length ratio maybe labeled W₂/L₂. However, it will be understood that the index merelydistinguishes the different ratios as a whole from one another, but doesnot necessarily imply anything about the specific channel widths and/orchannel lengths of the ratios. Thus, two transistors may have the samewidth to length ratio as each other, and yet have different channelwidths or channel lengths from one another. Similarly, two transistormay have different width to length ratios, and yet have the same channelwidths or the same channel lengths as one another. Thus, for example, ifa first transistor has the first ratio W₁/L₁ and a second transistoralso has the first ratio W₁/L₁, that does not imply that the channelwidth or the channel length of the two transistors must necessarily bethe same-it only implies that the ratios for the two transistors are thesame. As another example, if a first transistor has the first ratioW₁/L₁ and a second transistor has the W₂/L₂, that does not imply thatthe channel widths or channel lengths of the two transistors cannot bethe same-it only implies that the ratios for the two transistors aredifferent.

REFERENCE SIGNS LIST

-   10 organic EL display device-   20 unit pixel (pixel circuit)-   21 organic EL element-   22 drive transistor-   23 writing transistor-   24 storage capacitor-   25 auxiliary capacitor-   30 pixel array unit-   31(31 ₁ to 31 _(m)) scanning line-   32(32 ₁ to 32 _(m)) power supplying line-   33(33 ₁ to 33 _(n)) signal line-   34 common power supply line-   40 writing scanning unit-   50 power supplying scanning unit-   60 signal output unit-   70 display panel

1. A display unit comprising: a plurality of sub-pixels, each includinga light emitting element, a capacitor, a first transistor configured towrite a signal potential to the capacitor, and a second transistorconfigured to provide a drive current to the light emitting elementbased on a voltage stored in the capacitor, wherein the first transistorof each of the plurality of sub-pixels has a width-to-length ratio W/L,and a width to length ratio W₁/L₁ of a first sub-pixel of the pluralityof sub-pixels is different than a width-to-length ratio W₂/L₂ of asecond sub-pixel of the plurality of sub-pixels.
 2. The display unit ofclaim 1, wherein the plurality of sub-pixels are arranged in a matrix ofrows and columns, and the first sub-pixel and the second sub-pixel arelocated in a same row as one another.
 3. The display unit of claim 1,further comprising: scanning lines, each being connected to respectivegate electrodes of the first transistors of some of the plurality ofsub-pixels, wherein the first transistor of the first sub-pixel and thefirst transistor of the second sub-pixel are connected to the samescanning line as one another.
 4. The display unit of claim 1, whereinthe first sub-pixel emits light of a first color and the secondsub-pixel emits light of a second color.
 5. The display unit of claim 4,wherein the first color is red and the second color is green.
 6. Thedisplay unit of claim 4, wherein the first color is white and the secondcolor is green.
 7. The display unit of claim 4, wherein awidth-to-length ratio of each of the plurality of sub-pixels that emitslight of the first-color equals W₁/L₁, and a width-to-length ratio ofeach of the plurality of sub-pixels that emits light of the second-colorequals W₂/L₂.
 8. The display unit of claim 1, wherein the plurality ofsub-pixels each emit light in one of N colors, where N>1, each of the Ncolors has a different width-to-length ratio W_(i)/L_(i) correspondingthereto, where i={1, 2, . . . , N}, and for each of the N colors, awidth-to-length ratio of each of the plurality of sub-pixels that emitslight of the i-th color equals W_(i)/L_(i).
 9. The display unit of claim8, wherein the N colors include white, red, green, and blue, awidth-to-length ratio W₁/L₁ corresponds to white, a width-to-lengthratio W₂/L₂ corresponds to red, a width-to-length ratio W₃/L₃corresponds to green, a width-to-length ratio W₄/L₄ corresponds to blue,and W₁/L₁<W₂/L₂<W₄/L₄.
 10. The display unit of claim 8, wherein the Ncolors include red, green, and blue, a width-to-length ratio W₁/L₁corresponds to red, a width-to-length ratio W₂/L₂ corresponds to green,and a width-to-length ratio W₃/L₃ corresponds to blue, andW₁/L₁<W₂/L₂<W₂/L₃.
 11. An electronic apparatus comprising: a displayunit that includes a plurality of sub-pixels, each including a lightemitting element, a capacitor, a first transistor configured to write asignal potential to the capacitor, and a second transistor configured toprovide a drive current to the light emitting element based on a voltagestored in the capacitor, wherein the first transistor of each of theplurality of sub-pixels has a width-to-length ratio W/L, and a width tolength ratio W₁/L₁ of a first sub-pixel of the plurality of sub-pixelsis different than a width-to-length ratio W₂/L₂ of a second sub-pixel ofthe plurality of sub-pixels.
 12. The electronic apparatus of claim 11,wherein the plurality of sub-pixels are arranged in a matrix of rows andcolumns, and the first sub-pixel and the second sub-pixel are located ina same row as one another.
 13. The electronic apparatus of claim 11,further comprising: scanning lines, each being connected to respectivegate electrodes of the first transistors of some of the plurality ofsub-pixels, wherein the first transistor of the first sub-pixel and thefirst transistor of the second sub-pixel are connected to the samescanning line as one another.
 14. The electronic apparatus of claim 11,wherein the first sub-pixel emits light of a first color and the secondsub-pixel emits light of a second color.
 15. The electronic apparatus ofclaim 14, wherein the first color is red and the second color is green.16. The electronic apparatus of claim 14, wherein the first color iswhite and the second color is green.
 17. The electronic apparatus ofclaim 14, wherein a width-to-length ratio of each of the plurality ofsub-pixels that emits light of the first-color equals W₁/L₁, and awidth-to-length ratio of each of the plurality of sub-pixels that emitslight of the second-color equals W₂/L₂.
 18. The electronic apparatus ofclaim 11, wherein the plurality of sub-pixels each emit light in one ofN colors, where N>1, each of the N colors has a differentwidth-to-length ratio W_(i)/L_(i) corresponding thereto, where i={1, 2,. . . , N}, and for each of the N colors, a width-to-length ratio ofeach of the plurality of sub-pixels that emits light of the i-th colorequals W_(i)/L_(i).
 19. The electronic apparatus of claim 18, whereinthe N colors include white, red, green, and blue, a width-to-lengthratio W₁/L₁ corresponds to white, a width-to-length ratio W₂/L₂corresponds to red, a width-to-length ratio W₃/L₃ corresponds to green,a width-to-length ratio W₄/L₄ corresponds to blue, andW₁/L₁<W₂/L₂<W₃/L₃<W₄/L₄.
 20. The electronic apparatus of claim 18,wherein the N colors include red, green, and blue, a width-to-lengthratio W₁/L₁ corresponds to red, a width-to-length ratio W₂/L₂corresponds to green, and a width-to-length ratio W₃/L₃ corresponds toblue, and W₁/L₁<W₂/L₂<W₃/L₃.